U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Day Three

acus01 kwns 051923 
Storm Prediction Center ac 051921 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0121 PM CST Friday Feb 05 2016 

Valid 052000z - 061200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms are possible over the Pacific northwest 
coast...mainly tonight. 


No changes to 1630z necessary. 

.Darrow.. 02/05/2016 

Previous discussion... /issued 1021 am CST Friday Feb 05 2016/ 

In the wake of a cold front...which has advanced east of the 
Atlantic Seaboard and through much of the Gulf of Mexico...generally 
dry and/or stable conditions are prevalent across much of the 
nation. Little change is expected through the remainder of today 
and tonight across most areas. 

..Pacific northwest... 
One exception may be across parts of the Pacific northwest coast 
this evening into the overnight hours...as a vigorous short wave 
trough migrates inland off the eastern Pacific...around the crest of 
larger-scale middle/upper ridging. Forecast soundings suggest that 
steepening lapse rates associated with strong middle-level cooling 
/including to around or below -30c at 500 mb/ may contribute to 
thermodynamic profiles conducive to thunderstorm development. This 
is expected to be mostly confined to the lower elevations west of 
the northern Cascades during the 06/03-09z time frame. It appears 
that this will coincide with substantial strengthening of Lower/Middle 
tropospheric wind fields accompanying a 100+ knots 500 mb jet streak. 
While some convective enhancement of surface gusts /associated with 
downward momentum Transfer/ is possible...the risk for vigorous 
thunderstorm development still appears too negligible for even 5 
percent severe probabilities. 

Strong middle-level cooling /including to around -30c at 500 mb/... 
accompanying a vigorous short wave trough digging to the southeast 
of the central and southern rockies...may contribute to weak 
Lower/Middle tropospheric destabilization across parts of north central 
through southeast Texas late this evening into the overnight hours. 
This probably will be sufficient to support at least some convective 
development. But...with low-level moisture limited due to a lack of 
a substantive return flow off the Gulf of Mexico...it remains 
unclear whether thermodynamic profiles will become conducive to 
charge separation...and an appreciable risk for lightning. At this 
time...the risk for thunderstorms still seems to remain below the 
minimum 10 percent threshold for a categorical thunderstorm 


Mesoscale Discussion

acus11 kwns 051713 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 051712 

Mesoscale discussion 0092 
National Weather Service Storm Prediction Center Norman OK 
1112 am CST Friday Feb 05 2016 

Areas affected...coastal Maine and New Hampshire 

Concerning...heavy snow 

Valid 051712z - 052315z 

Summary...heavy snow...with rates around 1 inch/hr...will spread 
northeastward across coastal Maine and New Hampshire through 23z before diminishing. 

Discussion...17z rap mesoanalysis estimates a 1005 mb surface low to the 
southeast of coastal Massachusetts. As a shortwave trough evident on water vapor 
satellite imagery now over the East Coast moves quickly northeastward to the 
coastal Canadian provinces by tonight...large-scale lift attendant 
to the trough will encourage deepening of the surface low as it develops 
northeastward as well. Banded heavy snowfall ongoing across much of coastal 
New England is associated with strong middle-level frontogenesis... 
which will translate quickly northeastward with the overall system motion 
through the afternoon and early evening. Thermal profiles across 
coastal Maine/New Hampshire will remain cold enough to support all snow. A deep 
saturated profile through most of the troposphere per 12z observed 
soundings at kokx and kgyx combined with strong vertical motion 
associated with the middle-level frontogenesis indicate snowfall rates 
around 1 inch/hour will be common for at least a few hours. Given the 
strength of the upper forcing and reported snowfall totals across Massachusetts 
within enhanced reflectivity bands on the kbox radar...locally 
higher rates up to 2 inches/hour will be possible. Snowfall rates 
should decrease in intensity by 22-23z as the upper trough and surface 
low continue to move away from coastal Maine. 

.Gleason.. 02/05/2016 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 43107056 42887086 43107136 43747080 44486995 45366731 
45056686 44666701 44086847 43726968 43407023 43107056